The present invention relates to a chuck for turning machines, comprising radially displaceable master or clamping jaws each movable by means of a respective key bar which is guided in the chuck body tangentially to the axis of turning, with the key bars being provided with splined strips by which they engage teeth of the associated jaws and being displaceable to an extent such that, for removing the jaws, the splined strips come into a position in which they are disengaged from the teeth of the jaws. The invention further relates to a purposeful and advantageous development of the design of such a key bar chuck.